The present invention relates generally to medical apparatus and procedures, and more particularly to apparatus and a method which attaches a spinal-column buttress plate to two vertebral bodies of a spinal column of a medical patient.
Conventional medical procedures include attaching together (sometimes called fusing) first and second vertebral bodies of a spinal column (such as adjacent first and second cervical vertebral bodies of the cervical column portion of the spinal column) of a medical patient. A spinal-vertebral buttress plate (such as a cervical-vertebral buttress plate) of appropriate length is obtained. The buttress plate is positioned on the anterior side of the first and second vertebral bodies. The buttress plate comes with pre-drilled holes. Using first and second holes, of the positioned buttress plate, which are aligned over the first vertebral body, first and second starter holes are marked and drilled on the anterior cortex of the first vertebral body. Using third and fourth holes, of the positioned buttress plate, which is aligned over the second vertebral body, third and fourth starter holes are marked and drilled on the anterior cortex of the second vertebral body. A first bone screw is inserted in the first hole and a second bone screw is inserted in the second hole of the buttress plate and threaded into the corresponding starter hole in the anterior cortex of the first vertebral body, and a third bone screw is inserted in the third hole and a fourth bone screw is inserted in the fourth hole of the buttress plate and threaded into the corresponding starter hole in the anterior cortex of the second vertebral body. With the four bone screws securing the spinal-column buttress plate to the first and second vertebral bodies, the first and second vertebral bodies are thereby attached together (or fused) preventing their relative movement. Attachment problems arise when the pre-drilled holes of the spinal-column buttress plate are only alignable over a non-optimum area of the first and/or second vertebral body.
What is needed is a spinal-column buttress plate assembly (such as a cervical-column buttress plate assembly) and a method for attachment which provides better attachment of the spinal-column (e.g., cervical-column) buttress plate to the first and second vertebral bodies (e.g., the first and second cervical vertebral bodies.
A first expression of a preferred embodiment of the invention is for a cervical-column buttress plate assembly for fusing together first and second cervical vertebral bodies of a cervical column of a medical patient. The buttress plate assembly includes a first cervical-vertebral buttress plate, a first screw assembly, and a second screw assembly. The cervical-vertebral buttress plate has an elongated slot with opposing and serrated edges. The first screw assembly includes a first bone screw and a first inner screw. The first bone screw has an internally-threaded hole, has an externally-threaded shaft which is threadably insertable into the first cervical vertebral body of the cervical column of the medical patient and which has an expandable tip, and has an expandable head which is attached to the shaft and which has external teeth. The second screw assembly has a second bone screw and a second inner screw. The second bone screw has an internally-threaded hole, has an externally-threaded shaft which is threadably insertable into the second cervical vertebral body of the cervical column of the medical patient and which has an expandable tip, and has an expandable head which is attached to the shaft and which has external teeth. The first and second inner screws are engageable, respectively, in the internally-threaded holes of the first and second bone screws to expand the tips of the first and second bone screws against the first and second cervical vertebral bodies and to expand the heads of the first and second bone screws to engage the external teeth of the heads of the first and second bone screws against the opposing and serrated edges of the elongated slot of the buttress plate after the elongated slot of the buttress plate has been disposed to enclose the heads of the first and second bone screws after the first and second bone screws have been threadably inserted into the first and second vertebral bodies.
A second expression of a preferred embodiment of the invention is for a spinal-column buttress plate assembly for attaching together first and second vertebral bodies of a spinal column of a medical patient. The buttress plate assembly includes a spinal-vertebral buttress plate, a first screw assembly, and a second screw assembly. The buttress plate has an elongated slot with opposing edges. The first screw assembly includes a first bone screw and a first inner screw. The first bone screw has an internally-threaded hole, has a shaft which is insertable into the first vertebral body of the spinal column of the medical patient, and has an expandable head which is attached to the shaft and which has a first unexpanded state and a first expanded state. The head of the first bone screw is small enough to pass through the elongated slot in the first unexpanded state but not in the first expanded state. The second screw assembly includes a second bone screw and a second inner screw. The second bone screw has an internally-threaded hole, has a shaft which is insertable into the second vertebral body of the spinal column of the medical patient, and has an expandable head which is attached to the shaft and which has a second unexpanded state and a second expanded state. The head of the second bone screw is small enough to pass through the elongated slot in the second unexpanded state but not in the second expanded state. The first and second inner screws are engageable, respectively, in the internally-threaded holes of the first and second bone screws to expand the heads of the first and second bone screws to engage the heads of the first and second bone screws against the opposing edges of the elongated slot of the buttress plate after the elongated slot of the buttress plate has been disposed to enclose the heads of the first and second bone screws after the first and second bone screws have been inserted into the first and second vertebral bodies.
An alternate preferred embodiment is identical to the previously-described second expression of the preferred embodiment except that the buttress plate has first and second elongated slots with the first bone screw associated with the first elongated slot and with the second bone screw associated with the second elongated slot.
A first expression of a method of the invention is for fusing together first and second vertebral bodies of a spinal column of a medical patient and includes steps a) through h). Step a) includes obtaining first and second bone screws each having an internally-threaded hole, each having a shaft with an expandable tip, and each having an expandable head attached to the shaft and having external teeth. Step b) includes obtaining first and second inner screws engageable, respectively, with the internally-threaded holes of the first and second bone screws to expand the tips and the heads of the first and second bone screws. Step c) includes obtaining a buttress plate having an elongated slot with opposing and serrated edges. Step d) includes inserting the first bone screw into the first vertebral body of the spinal column of the medical patient with the head of the first bone screw protruding above the first vertebral body. Step e) includes inserting the second bone screw into the second vertebral body of the spinal column of the medical patient with the head of the second bone screw protruding above the second vertebral body. Step f) includes placing the buttress plate on the first and second vertebral bodies with the heads of the first and second bone screws disposed in the elongated slot of the buttress plate. Step g) includes threading the first inner screw into the internally-threaded hole of the first bone screw expanding the tip of the first bone screw against the first vertebral body and expanding the head of the first bone screw to engage the external teeth of the head of the first bone screw against the opposing and serrated edges of the elongated slot of the buttress plate. Step h) includes threading the second inner screw into the internally-threaded hole of the second bone screw expanding the tip of the second bone screw against the second vertebral body and expanding the head of the second bone screw to engage the external teeth of the head of the second bone screw against the opposing and serrated edges of the elongated slot of the buttress plate.
A second expression of a method of the invention is for attaching together first and second vertebral bodies of a spinal column of a medical patient and includes steps a) through h). Step a) includes obtaining first and second bone screws each having an internally-threaded hole, each having a shaft, and each having an expandable head attached to the shaft. Step b) includes obtaining first and second inner screws engageable, respectively, with the internally-threaded holes of the first and second bone screws to expand the heads of the first and second bone screws. Step c) includes obtaining a buttress plate having an elongated slot with opposing edges. Step d) includes inserting the first bone screw into the first vertebral body of the spinal column of the medical patient with the head of the first bone screw protruding above the first vertebral body. Step e) includes inserting the second bone screw into the second vertebral body of the spinal column of the medical patient with the head of the second bone screw protruding above the second vertebral body. Step f) includes placing the buttress plate on the first and second vertebral bodies with the heads of the first and second bone screws disposed in the elongated slot of the buttress plate. Step g) includes threading the first inner screw into the internally-threaded hole of the first bone screw expanding the head of the first bone screw to engage the head of the first bone screw against the opposing edges of the elongated slot of the buttress plate. Step h) includes threading the second inner screw into the internally-threaded hole of the second bone screw expanding the head of the second bone screw to engage the head of the second bone screw against the opposing edges of the elongated slot of the buttress plate.
An alternate second expression of a method of the invention is identical to the previously-described second expression of a method of the invention except that the buttress plate has first and second elongated slots with the first bone screw associated with the first elongated slot and with the second bone screw associated with the second elongated slot.
A third expression of a method of the invention is for attaching together first and second vertebral bodies of a spinal column of a medical patient and includes steps a) through e). Step a) includes obtaining first and second bone screws. Step b) includes obtaining a buttress plate. Step c) includes inserting the first bone screw into the first vertebral body of the spinal column of the medical patient. Step d) includes inserting the second bone screw into the second vertebral body of the spinal column of the medical patient. Step e) includes attaching the buttress plate to the first and second bone screws after performing steps a) through d).
Several benefits and advantages are derived from the invention. The apparatus and method of the invention allows a physician to choose an optimum location for the first bone screw on the first vertebral body (e.g., on the first cervical vertebral body) and to choose an optimum location for the second bone screw on the second vertebral body (e.g., on the second cervical vertebral body) for maximum attachment strength and mechanical stability. This is accomplished by first installing the bone screws on the vertebral bodies and then securing the buttress plate to the installed bone screws. In comparison, the prior art forces the physician to use pre-drilled holes in the buttress plate which often provide less than optimum attachment locations (providing less attachment strength and less mechanical stability) for the bone screws to be installed in the vertebral bodies.